Atrazine Degradation Research Articles

Degradation of atrazine, glyphosate, and 2,4-D in soils collected from two contrasting crop rotations in Southwest Chaco, Argentina

Argentina stands as one of the leading consumers of herbicides. In a laboratory incubation experiment, the persistence and production of degradation metabolites of Atrazine, 2,4-D, and Glyphosate were investigated in a loamy clay soil under two contrasting agricultural practices: continuous soybean cultivation (T1) and intensified rotations with grasses and legumes (T2). The soils were collected from a long-term no-till trial replicating the influence of the meteorological conditions in the productive region. The soil was enriched with diluted concentrations of 6.71, 9.95, and 24 mg a.i./kg-1 of soil for the respective herbicides, equivalent to annual doses commonly used in the productive region. Samples were taken at intervals of 0, 0.5, 1, 2, 4, 6, 8, 16, 32, and 64 days, and analysis was conducted using high-resolution liquid chromatography UPLC MS/MS. An optimal fit to the first-order kinetic model was observed for each herbicide in both rotations, resulting in relatively short half-lives. Intensified crop sequences favored the production of biotic degradation metabolites. The impact of the high frequency of soybean cultivation revealed a trend of soil acidification and a reduced biological contribution to attenuation processes in soil contamination.

Advanced oxidation treatment of aqueous atrazine by fixed-bed reactor packed with carbon-supported molybdenum disulfide

MoS2/carbon composites were prepared by affixing MoS2 onto carbon particulates and used as packing materials to establish persulfate advanced oxidation fixed-bed reactors (PS-FBR) for effective continuous-flow degradation of organic pollutants. Since MoS2 was a co-catalyst in accelerating the conversion of Fe3+ to Fe2+, an improved degradation performance against organic pollutants such as atrazine (ATZ) was achieved in this PS/Fe2+/MoS2-FBR. Cost-effective materials of granular carbon, needle carbon, quartz particles, and MoS2 with different morphologies were compared during the preparation of MoS2/carrier composites. The results indicated that a higher adsorption capacity of both carriers and MoS2 was more plausible for ATZ degradation in FBR. After the systematic investigation of reaction conditions, a removal efficiency of 99 % for ATZ was achieved at pH 3–7, 2 mg/L Fe2, 2 mM PS, flow rate of 2 mL/min (cross-sectional area of 1.33 cm2). Meanwhile, this PS/Fe2+/MoS2-FBR could be continuously operated for over 5 days with removal efficiency above 90 %. Importantly, a low Fe2+ concentration of 2 mg/L was sufficient in this system, which could limit the formation of iron sludge and ensure long-term operation.

Interplay of xenobiotic-degrading and antibiotic-resistant microorganisms among the microbiome found in the air, handrail, and floor of the subway station

Investigating the quality of the subway environment, especially regarding antibiotic resistance genes (ARGs) and xenobiotics, conveys ecological and health impacts. In this study, compositions and relations of microorganisms harboring ARGs and xenobiotic degradation and metabolism genes (XDGs) in the Sukhumvit subway station (MRT-SKV) in Bangkok was assessed by analyzing the taxonomic and genetic diversity of the microbiome in the air and on the surfaces of floor and handrail. The major bacteria in the MRT-SKV (including Moraxella, which was abundant in the bioaerosol and handrail samples, and Staphylococcus, which was abundant in the bioaerosol samples) were found to contain both ARGs and XDGs. The co-abundance correlation network revealed notable relationships among bacteria harboring antibiotic resistance genes (ARGs) and xenobiotic degradation genes (XDGs). Significant associations were observed between ARGs linked to glycopeptide and fluoroquinolone resistance and genes associated with benzoate, styrene, and atrazine degradation pathways, as well as between ARGs related to cephamycin, cephalosporin, and MLS resistance and XDGs associated with the cytochrome P450-dependent drug metabolism pathway. These correlations suggested that selective pressure exerted by certain xenobiotics and antibiotics can simultaneously affect both ARGs and XDGs in the environment and should favor correlations and co-survival among ARG- and XDG-containing bacteria in the environments. The correlations may occur via shared mechanisms of resistance to both xenobiotics and antibiotics. Finally, different correlation pairs were seen in different niches (air, handrail, floor) of the subway environment or different geolocations. Thus, the relationship between ARG and XDG pairs most likely depends on the unique characteristics of the niches and on the prominent types of xenobiotics and antibiotics in the subway environment. The results indicated that interactions and connections between microbial communities can impact how they function. These microorganisms can have profound effects on accumulation of xenobiotics and ARGs in the MRT-SKV.

Comparative study of the efficiency of conventional and green-prepared iron nanoparticles for catalytic ozonation

This study aimed at the preparation of green and conventionally prepared iron nanoparticles (Fe-C-NPs), their characterization and application as catalysts of ozonation to remove emerging contaminants and disinfection. It is the first time that a study has compared the chemical and morphological characteristics of Fe-C-NPs and related them to their efficiency as catalysts in ozonation. Green Fe-C-NPs were prepared with eucalyptus and mulberry leaves extract and the conventional Fe-C-NPs prepared using ammonia as reducing agent. The green synthesis routes are low cost and environmental friendly, thereby reducing the risk of harmful effects of toxic chemicals and derivative compounds. The Fe-C-NPs were characterized by FTIR, SEM, XRD, XPS and VSM, and were applied in the degradation of malachite green, methylene blue, sulfamethoxazole, atrazine, and acetaminophen in ultrapure water and secondary effluent as well as in the inactivation of disinfection indicators. As expected, the implementation of Fe-C-NPs in catalytic ozonation resulted in enhanced efficacy compared to ozonation alone. However, the green Fe-C-NPs showed equivalent or better efficiency compared to the conventionally Fe-C-NPs, showing better efficiencies in cleaner water matrices. When applied to remove micropollutants and promote disinfection in secondary effluents, the green Fe-C-NPs showed equivalent efficiencies in comparison with conventional Fe-C-NPs. It highlights that nanomaterials produced by green routes can be an alternative to traditional nanomaterials that use of toxic reagents on its production.

Preparation and activity study of Ruoqiang jujube polysaccharide copper chelate.

Background: Polysaccharide metal chelate exhibit both immunoregulatory activity and metal element supplementation effects. Methods: In this study, Ruoqiang jujube polysaccharide copper chelate (RJP-Cu) was prepared and the preparation conditions were optimized using the response surface method. Subsequently, RJP-Cu was administered to lambs to evaluate its impact on growth performance, copper ion (Cu2+) supplementation, immune enhancement, and intestinal flora was evaluated. Results: The results indicated that optimal RJP-Cu chelation conditions included a sodium citrate content of 0.5 g, a reaction temperature of 50°C, and a solution pH of 8.0, resulting in a Cu2+ concentration of 583°mg/kg in RJP-Cu. Scanning electron microscopy (SEM) revealed significant structural changes in RJP before and after chelation. RJP-Cu displaying characteristic peaks of both polysaccharides and Cu2+ chelates. Blood routine indexes showed no significant differences among the RJP-Cu-High dose group (RJP-Cu-H), RJP-Cu-Medium dose group (RJP-Cu-M), RJP-Cu-low dose group (RJP-Cu-L) and the control group (p > 0.05). However, compared with the control group, the RJP-Cu-H, M, and L dose groups significantly enhanced lamb production performance (p < 0.05). Furthermore, RJP-Cu-H, M, and L dose groups significantly increased serum Cu2+ concentration, total antioxidant capacity (T-AOC), catalase (CAT), and total superoxide dismutase (T-SOD) contents compared with control group (p < 0.05). The RJP-Cu-H group exhibited significant increases in serum IgA and IgG antibodies, as well as the secretion of cytokines IL-2, IL-4, and TNF-α compared to the control group (p < 0.05). Furthermore, RJP-Cu-H group increased the species abundance of lamb intestinal microbiota, abundance and quantity of beneficial bacteria, and decrease the abundance and quantity of harmful bacteria. The RJP-Cu-H led to the promotion of the synthesis of various Short Chain Fatty Acids (SCFAs), improvements in atrazine degradation and clavulanic acid biosynthesis in lambs, while reducing cell apoptosis and lipopolysaccharide biosynthesis. Conclusion: Thus, these findings demonstrate that RJP-Cu, as a metal chelate, could effectively promote lamb growth performance, increase Cu2+ content, and potentially induce positive immunomodulatory effects by regulating antioxidant enzymes, antibodies, cytokines, intestinal flora, and related metabolic pathways.

Boosted Photocatalytic Degradation of Atrazine Using Oxygen-Modified g-C3N4: Investigation of the Reactive Oxygen Species Interconversion.

Elaborating the specific reactive oxygen species (ROS) involved in the photocatalytic degradation of atrazine (ATZ) is of great significance for elucidating the underlying mechanism. This study provided conclusive evidence that hydroxyl radicals (·OH) were the primary ROS responsible for the efficient photocatalytic degradation of ATZ, thereby questioning the reliability of widely adopted radical quenching techniques in discerning authentic ROS species. As an illustration, oxygen-modified g-C3N4 (OCN) was prepared to counteract the limitations of pristine g-C3N4 (CN). Comparative assessments between CN and OCN revealed a remarkable 10.44-fold improvement in the photocatalytic degradation of ATZ by OCN. This enhancement was ascribed to the increased content of C-O functional groups on the surface of the OCN, which facilitated the conversion of superoxide radicals (·O2-) into hydrogen peroxide (H2O2), subsequently leading to the generation of ·OH. The increased production of ·OH contributed to the efficient dealkylation, dechlorination, and hydroxylation of ATZ. Furthermore, toxicity assessments revealed a significant reduction in ATZ toxicity following its photocatalytic degradation by OCN. This study sheds light on the intricate interconversion of ROS and offers valuable mechanistic insights into the photocatalytic degradation of ATZ.

Carbon nitride with grafted molecular as electron acceptor and active site to achieve efficient photo-activated peroxymonosulfate for organic pollutants removal

The effective activation of peroxymonosulfate (PMS) by polymer carbon nitride (PCN) is hampered by the unpredictable movement and rapid recombination of photocarriers. In this study, niacin served as a beneficial modifier to help constructed the directional electron transfer pathway from the center to the edge in the synthesized PCN catalyst (UCNNA) for efficient PMS activation. The UCNNA/PMS/vis shows the highest kinetic constants (0.050 min−1), which is 2.9-fold increase over the PCN/PMS/vis. The experiments and theoretical calculations indicated that niacin as electron acceptor group prevents the recombination of photocarriers in-plane. Simultaneously, niacin can serve as PMS adsorption site, further facilitating electron transfer and the 1O2 generation. Mass spectrometry analysis and Fukui index calculations confirm the priority of lateral chain oxidation (1O2 attack site) during atrazine degradation. These results provide new insights into rational design of metal-free catalysts/PMS/vis system, as well as providing guidance and theoretical support for atrazine degradation mechanisms.

Examining the Role of Material Science in Atrazine Herbicide Biodegradation by Pseudomonas putida MTCC 2252

Atrazine is a chlorinated herbicide of the triazine class. It is used to prevent pre-emergence broadleaf weeds in crops such as maize (corn), soybean and sugarcane and on turf, such as golf courses and residential lawns. Atrazine's primary manufacturer is Syngenta and it is one of the most widely used herbicides in the United States, Canadian, and Australian agriculture. The bacteria used for the bio degradation of Atrazine is Pseudomonas putida. In this study, we report the biodegradation of Atrazine at high initial concentrations. The biodegradation of this Atrazine was investigated using Pseudomonas putida. For Pseudomonas putida optimization parameters like Contact time, Ph, Initial concentration, Temperature, Inoculum volume, Carbon source, Nitrogen source

Characteristics of bacterial community and extracellular enzymes in response to atrazine application in black soil

The ecological functioning of black soil largely depends on the activities of various groups of microorganisms. However, little is known about how atrazine, a widely used herbicide with known harmful effects on the environment, influences the microbial ecology of black soil, and the extracellular enzymes related to the carbon, nitrogen and phosphorus cycles. Here, we evaluated the change in extracellular enzymes and bacterial community characteristics in black soil after exposure to various concentrations of atrazine. Low concentrations of applied atrazine (10 – 20 mg kg−1) were almost completely degraded after 120 days. At high concentrations (80 – 100 mg kg−1), about 95% of the applied atrazine was degraded over the same period. Additionally, linear fitting of data indicated that the total enzymatic activity index (TEI) and bacterial α-diversity index were negatively correlated with atrazine applied concentration. The atrazine had a greater effect on bacterial beta diversity after 120 days, which differentiated species clusters treated with low and high atrazine concentrations. Soil bacterial community structure and function were affected by atrazine, especially at high atrazine concentrations (80 – 100 mg kg−1). Key microorganisms such as Sphingomonas and Nocardioides were identified as biomarkers for atrazine dissipation. Functional prediction indicated that most metabolic pathways might be involved in atrazine dissipation. Overall, the findings enhance our understanding of the factors driving atrazine degradation in black soil and supports the use of biomarkers as indicators of atrazine dissipation.

Organic pollutants degradation by glyoxylic acid boosted Fenton-like system: An overlooked Fe(III)/Fe(II) cycles with low-molecular-weight organic acid

Herein, glyoxylic acid (GA) was incorporated into the Fenton-like (Fe(III)/H2O2) system to rigorously examine its impact on the degradation of organic pollutants. It was found that the degradation efficiencies of atrazine (ATR), ofloxacin (OFL), rhodamine B (RhB), and carbamazepine (CBZ) in the Fe(III)/GA/H2O2 system were ∼95%, and the apparent ATR degradation rate constant (1.60 × 10−2 min−1) was 4-fold as high as that (0.40 × 10−2 min−1) in the Fe(III)/H2O2 system at pH 3.6. The UV–vis spectral and cyclic voltammetry (CV) analyses demonstrated that GA could be used as a ligand and reductant to coordinate and reduce Fe(III), thereby promoting the Fe(III)/Fe(II) cycles in the Fenton-like process. Testing results for reactive oxygen species (ROS) confirmed that superoxide ions (•O2–) and hydroxyl radicals (•OH) respectively undertake the Fe(III)/Fe(II) cycles and ATR degradation in the Fe(III)/GA/H2O2 system. The reaction stoichiometric efficiencies (RSE) in the Fe(III)/GA/H2O2 system (37.5%–76.9%) were significantly higher than those (2.8%–4.9%) in the Fe(III)/H2O2 system within 180 min, and the maximum concentration of •OH in the Fe(III)/GA/H2O2 system was 4.6 times that in the Fe(III)/H2O2 system. A series of the important variables were optimized in detail, including solution pH, GA dosage, amount of Fe(III) and H2O2. These findings provide compelling evidence for the non-negligible role of GA in the processes of organic pollutants degradation based on the Fe(III)/Fe(II) cycles and radicals generation in the Fenton-like system.

Self-cycling of Fe(II)/Fe(III) and the important role of Fe(IV) in promoting efficient degradation of atrazine (ATZ) in a wider pH range

The Fe(II)/Fe(III)@C catalysts were prepared by doping Fe2+ into MIL-101(Fe) as a template at high temperature. Through systematic and comprehensive characterization (SEM, XRD, FTIR, etc.), it was demonstrated that Fe elements were uniformly attached to the particle surface, providing excellent active sites for activation of peroxymonosulfate (PMS), and were successfully used for the degradation of atrazine (ATZ) in water. The effects of different environmental factors on the degradation of ATZ were investigated, and it was found that ATZ was still efficiently degraded (>95%) in a wide pH range (pH of 3–9). After quenching as well as ESR spectroscopic detection jointly suggested the contribution of substances that play a role in the system: 1O2 (71%) > ∙OH (32%) > SO4∙− (25%) > Fe(IV) (12.5%)> O2∙− (7%). After PMSO was used as a probe, the important role of Fe(IV) in the system was verified. Furthermore, the intermediates in the degradation of ATZ were detected by GC-MS and their toxicity was analyzed. Finally, two pathways of Fe(II)↔Fe(III) cycling were proposed in combination with the above experimental and computational contents, and multiple cycle tests including different contaminant tests were performed to verify the application potential of Fe(II)/Fe(III)@C-system. This work provides a research basis for the activation of MOF-derived carbon-based catalysts for the degradation of organic pollutants by PMS.

Understanding atrazine elimination via treatment of the enzyme-based Fenton reaction: Kinetics, mechanism, reaction pathway, and metabolites toxicity

The degradation kinetics and mechanism of atrazine (ATZ) via an enzyme-based Fenton reaction were investigated at various substrate concentrations and pH values. Toxicological assessment was conducted on ATZ and its degradation products, and the associated reaction pathway was examined. The in situ production of hydrogen peroxide (H2O2) was monitored within the range of 3–15 mM, depending on the increase in glucose concentration, while decreasing the pH to 3.2–5.1 (initial pH of 5.8) or 6.5–7.4 (initial pH of 7.7). The degradation efficiency of ATZ was approximately 2–3 times higher at an initial pH of 5.8 with lower glucose concentrations than at an initial pH of 7.7 with higher substrate concentrations during the enzyme-based Fenton reaction. The apparent pseudo-first-order rate constant for H2O2 decomposition under various conditions in the presence of ferric citrate was 1.9–6.3 × 10−5 s−1. The •OH concentration ([•OH]ss) during the enzyme-based Fenton reaction was 0.5–4.1 × 10−14 M, and the second-order rate constant for ATZ degradation was 1.5–3.3 × 109 M−1 s−1. ATZ intrinsically hinders the growth and development of Arabidopsis thaliana, and its inhibitory effect is marginal, depending on the reaction time of the enzyme-based Fenton process. The ATZ transformation during this process occurs through dealkylation, hydroxylation, and dechlorination via •OH-mediated reactions. The degradation kinetics, mechanism, and toxicological assessment in the present study could contribute to the development and application of enzyme-based Fenton reactions for in situ pollutant abatement. Moreover, the enzyme-based Fenton reaction could be an environmentally benign and applicable approach for eliminating persistent organic matter, such as herbicides, using diverse H2O2-producing microbes and ubiquitous ferric iron with organic complexes.

Degradation of atrazine by electro-peroxone enhanced by Fe and N co-doped carbon nanotubes with simultaneous catalysis of H2O2 and O3

Fe and N co-doped carbon nanotubes (Fe-N-CNT) was synthesized and attempted as efficient heterogeneous catalysts for simultaneous catalysis of H2O2 and O3 to improve electro-peroxone (Fe-N-CNT/EP) process efficiency for atrazine (ATZ) degradation. The removal and mineralization of ATZ was significantly enhanced, obtaining the degradation rate constant (k) by Fe-N-CNT/EP (0.23 min−1) about two times that of EP (0.12 min−1) owing to the formation of Fe0 and Fe-N coordination in Fe-N-CNT catalyst for co-catalysis of H2O2 and O3. The important factors such as applied current and ozone concentration were investigated, demonstrating that the optimized performance could be achieved at current of 30 mA and ozone concentration of 55 mg L−1. The oxidation capacity of Fe-N-CNT/EP maintained stably under wide pH range of 3∼7, obtaining the degradation rate constant 1.23–1.92 times that of EP and overcoming the defect of EP at acidic and neutral conditions. Capture experiments and electron paramagnetic resonance (EPR) experiments verified that .OH, generated by accelerating decomposition of H2O2/O3 and peroxone reaction, was the dominant active specie in Fe-N-CNT/EP. Besides, Fe-N-CNT showed high catalytic activity and good stability during six cycles. This work provides an efficient activator for enhanced EP process, exhibiting a promising prospect for water and wastewater purification.

The Cd immobilization mechanisms in paddy soil through ureolysis-based microbial induced carbonate precipitation: Emphasis on the coexisting cations and metatranscriptome analysis

Microbial induced carbonate precipitation (MICP) can immobilize metals and reduce their bioavailability. However, little is known about the immobilization mechanism of Cd in the presence of soil cations and the triggered gene expression and metabolic pathways in paddy soil. Thus, microcosmic experiments were conducted to study the fractionation transformation of Cd and metatranscriptome analysis. Results showed that bioavailable Cd decreased from 0.62 to 0.29 mg/kg after 330 d due to the MICP immobilization. This was ascribed to the increase in carbonate bound, Fe-Mn oxides bound, and residual Cd. The underlying immobilization mechanisms could be attributed to the formation of insoluble Cd-containing precipitates, the complexation and lattice substitution with carbonate and Fe, Mn and Al (hydr)oxides, and the adsorption on functional group on extracellular polymers of cell. During the MICP immobilization process, up-regulated differential expression urease genes were significantly enriched in the paddy soil, corresponding to the arginine biosynthesis, purine metabolism and atrazine degradation. The metabolic pathway of bacterial chemotaxis, flagellum assembly, and peptidoglycan biosynthesis and the expression of cadA gene related to Cd excretion enhanced Cd resistance of soil microbiome. Therefore, this study provided new insights into the immobilization mechanisms of Cd in paddy soils through ureolysis-based MICP process.

Amino acid promoted oxidation of atrazine by Fe3O4/persulfate

In the present study, we demonstrated that the presence of cysteine could remarkably enhance the degradation of atrazine by Fe3O4/persulfate system. The results of electron paramagnetic resonance (EPR) spectra confirmed the combination of cysteine and Fe3O4 exhibited much higher activity on activation of persulfate to generate more SO4•- and •OH than Fe3O4 alone. At pH of 3.0, SO4•- and •OH contributed to about 58.2 % and 41.8 % of atrazine removal respectively, while •OH gradually dominated the oxidation of atrazine from neutral condition to alkaline condition. The co-existing Cl− and HCO3− could quench SO4•-, resulting in the inhibition of atrazine degradation. The presence of low natural organic matters (NOM) concentration (0–2 mg L−1) could enhance the atrazine removal, and high concentration (>5 mg L−1) of NOM restrained the atrazine degradation. During the Cysteine/Fe3O4/Persulfate process, cysteine served as a complexing reagent and reductant. Through acidolysis and complexation, Fe3O4 could release dissolved and surface bound Fe2+, both of which contributed to the activation of persulfate together. Meanwhile, cysteine was not rapidly consumed due to a regeneration process, which was beneficial for maintaining Fe2+/Fe3+ cycle and constantly accelerating the activation of persulfate for atrazine degradation. The reused Fe3O4 and cysteine in the Cysteine/Fe3O4/Persulfate process exhibited high stability for the atrazine degradation after three cycles. The degradation pathway of atrazine included alkylic-oxidation, dealkylation, dechlorination-hydroxylation processes. The present study indicates the novel Cysteine/Fe3O4/Persulfate process might be a high potential for treatment of organic polluted water.

Treatment of Atrazine through Ozonation: Effect of Contact Time on COD and Atrazine Removal

In this work, degradation of atrazine, an herbicide, is explored through the advanced oxidation process of ozonation. Ozonation can degrade organic as well as inorganic compounds. The study evaluated and analyzed the effect of contact time of ozonation on concentration of atrazine removal as well as chemical oxygen demand (COD) removal of the treated sample. The study also analyzed the effect of initial pH on COD removal. The synthetic sample prepared was having an initial concentration of atrazine as 100 ppb with corresponding COD as 203mg/l. The atrazine removal efficiency was found to be increasing with the increase in ozonation time. Atrazine was observed to degrade more when the pH was alkaline. So, the initial pH was kept as 9.9 and the ozone dose was 9.8 mg/l. The optimum ozonation time was 40 minutes which resulted in COD removal of 55.40 % and atrazine removal of 36.33%. The results showed that atrazine is destroyed by ozone very rapidly.

S doping induces to promoted spatial separation of charge carriers on carbon nitride for efficiently photocatalytic degradation of atrazine

Atrazine (ATZ), as one of the most extensively employed organochlorine-based herbicides, exhibits persistence and environmental toxicity. Photocatalytic technology based on polymer carbon nitride is regarded as a sustainable and promising approach for the degradation of emerging organic pollutants. Regrettably, the inherent shortcomings of pure carbon nitride greatly limit its practical application. Herein, S-doped carbon nitride was elaborately constructed for efficient degradation of ATZ. The removal efficiency of ATZ by the optimal sample (0.052 min−1) is 3.25 times as that of pure carbon nitride (0.016 min−1). Experiments and DFT calculations show that S doping optimizes electronic structure of carbon nitride, which significantly enhances the spatial separation and transfer efficiency of photogenerated electrons and holes. Moreover, the reactive sites and degradation paths of ATZ were predicted by Fukui function and LC-MS determination. Our work provides an effective approach for the design of efficient photocatalysts to achieve efficient environmental remediation.

Assessing Biodegradation Processes of Atrazine in Constructed Wetland Using Compound-Specific Stable Isotope Analysis

To bridge the gap between lab-scale microcosm research and field application in the compound-specific stable isotope analysis (CSIA) of atrazine, we studied the characteristics of carbon and nitrogen isotope fractionation in the atrazine degradation processes within a constructed wetland. In the wetland, we observed multiple element (C, N) isotope fractionation parameters, such as kinetic isotope effects and dual isotope slopes. These parameters are very consistent with those observed in the cultivation of AtzA- or TrzN-harboring strains, suggesting a similarity in the pathway and reaction mechanism of atrazine biodegradation between the two settings. However, we recorded variable carbon (εC: −3.2 ± 0.6‰ to −4.3 ± 0.6‰) and nitrogen isotope fractionation (εN: 1.0 ± 0.3‰ to 2.2 ± 0.3‰) across different phases. This variance could lead to an over- or underestimation of the biodegradation extent of atrazine when employing the large or small enrichment factor of the carbon isotope. Intriguingly, the estimation accuracy improved considerably when using the enrichment factor (−4.6‰) derived from the batch cultivation of the pore water. This study advances the application of CSIA in tracking atrazine biodegradation processes in ecosystems, and it also underlines the importance of the careful selection and application of the enrichment factor in quantifying the intrinsic biodegradation of atrazine in ecosystems.

Carbon and hydrogen isotopic evidence for atrazine degradation by electro-activated persulfate: Radical contributions and comparisons with heat-activated persulfate

The activation ways of persulfate (PS) were dominate for pollutant degradation and energy consumption. For the first time, this research compared electro-activated PS and heat-activated PS from the perspective of isotope fractionation, in order to “fingerprinted” and precisely interpretate reaction contributions and degradation pathways. As results, PS can be electrochemically activated with atrazine (ATZ) removal rates of 84.8% and 88.8% at pH 4 and 7. The two-dimensional isotope plots (ɅC/H) values were 6.20 at pH 4 and 7.46 at pH 7, rather different from that of SO4·― -dominated process with ɅC/H value of −4.80 at pH 4 and -23.0 at pH 7, suggesting the weak contribution of SO4·―. ATZ degradation by electro-activated PS was controlled by direct electron transfer (DET) and ·OH radical, and ·OHPS (derived from PS activation) played the crucial role with contributing rate of 63.2%–69.1%, while DET and ·OHBDD (derived from electrolysis of H2O) contributed to 4.5–7.9% and 23.0%–30.8%, respectively. This was different from heat activation of PS, of which the latter was dominated by SO4·― with contributions of 83.9%–100%. The discrepant dominating reactive oxygen species should be responsible for their different degradation capabilities and pathways. This research provided isotopic interpretations for differences of PS activation mode, and further efforts can be made to realize the selective degradation by enhancing the specific reaction process.

In-situ self-assembled flower-like ZnIn2S4/CdIn2S4 composites with enhanced interfacial charge transfer and photocatalytic degradation of atrazine

In heterostructure photocatalysts, interface charge transfer is a crucial step in the photocatalytic process, so it is crucial to construct photocatalysts with high interface charge transfer efficiency. Here we report an in-situ self-assembled flower-like ZnIn2S4/CdIn2S4 (ZCIS) composites with excellent catalytic performance for atrazine (ATZ) degradation. The ZCIS-4 composite could degrade 99.82% of ATZ within 40 min, which showed 1.42 and 1.91 times better than blank ZnIn2S4 and CdIn2S4, respectively. The excellent catalytic performance is attributed to the built-in electric field in the in-situ self-assembled composite photocatalyst, which accelerates the rapid transfer of interfacial charges and the rapid separation of photogenerated electron hole pairs. The toxicity assessment shown that some intermediates exhibited decreased toxicities; however, the toxicities were still significant. Active radical capture experiments and electron spin resonance characterization demonstrated that h+, O2− were the main active free radicals. Differential charge density simulation calculations verified that interface photogenerated electrons were transported from CIS to the ZIS surface.